feature request: need a spark library to build data files offline and loaded directly into YDB

[chrislusf]

The use case is to serve read only large amount of data, which is a snapshot of machine learning results. The snapshot needs to update daily. Need a spark library to generate the files for YDB tables and indexes.

Ideally the files can be used by YDB directly, without any ingestion process. Preferably not CSV files because the CSV files need additional processing, impacting request latency.